Emergency Imaging of Brain Tumors: Tumor Classification
This video is the second video in an overview about the emergent approach to brain tumor imaging. The first video talked about the role of imaging in an emergent setting and how to approach cases. This tells you a little bit more about the common types of tumors you might encounter and how they are classified.
Common types of brain tumors. The most common brain tumors you may encounter are primary gliomas, meningioma, metastatic disease, and lymphoma. Calvarial tumors, or those centered in the skull, have a somewhat special differential.
Primary gliomas. The primary gliomas encompass all the grade 2, 3, and 4 oligodendrogliomas and astrocytomas. In 2016, the WHO started using genetic testing more to classify these tumors, and further refined these classifications in 2021. In general, tumors are first classified by whether they have isocitrate dehydrogenase (IDH) mutation. Mutated tumors tend to be lower grade astrocytomas and oligodendrogliomas. If they have 1p19q co-deletion, they are oligodendrogliomas, and otherwise astrocytomas. IDH wild type tumors are the most aggressive and include glioblastomas. Now, there are some tumors that have genetic features that make them a lot like glioblastomas.
Pearls about primary gliomas.
Higher grade tumors will be characterized by mor mass effect, hemorrhage, and enhancement, although you aren’t always going to be able to tell.
The term “multiforme” has fallen out of use, so you can just call them glioblastomas or GBM.
Gliosarcomas are a special subset of tumors that have features of both gliomas and sarcomas. They are often characterized by broad dural involvement or bone involvement, but sometimes you can’t tell.
Oligoastrocytoma is a deprecated term no longer used. If it has 1p19q codeletion and IDH mutation, it’s an oligodendroglioma.
Gliomatosis cerebri is no longer it’s own diagnosis but simply a pattern of brain involvement
Pearls about other common tumors
Meningiomas are the most common primary intracranial tumors. If you see an extra-axial tumor, it is likely a meningioma.
Metastatic disease is the overall most common intracranial tumor and should be suspected in older patients and those with other malignancies
Lymphoma can cause solid enhancing multifocal disease
Calvarial tumors have a special differential including meningioma, lymphoma, myeloma, and metastatic disease